This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. For this reporting period (4/1/06-4/30/07), an equivalent of 921 tilt-series were taken (a 1X2 montage was counted as 2 tilt-series). The average use is about 31.6 hours/week (1770 total hours in 56 weeks). Because the F30 microscope was more operational this year, the F20 usage dropped from last year. Training of five new users in both plastic and cryo tomography was performed on this microscope with great success (93.75 hours). We had 140.75 hours of service and development. From September 1, 2006, we started keeping track of hours by clocking in and out vs. just total hours logged. From that data, we have determined that about 22% of microscope time is after hours (5pm-8am M-F and weekends). Figure 1 illustrates F20 usage. Plastic section tomography (including montaging), closely followed by cryo imaging (single particle and evaluation of sample quality), regular EM work (pre-screening of grids, negative stain samples, serial section work, single-particle work, and immuno-EM) comprised the largest use of the F20, followed by cryo tomography, service, development (hardware and software) and training of new users. Figure 2 illustrates the distribution of tomography work done (a total of 921 tilt series taken).